1. Field of the Invention
This invention pertains to mirrors, and more specifically to a rearview mirror to be mounted in any convenient location interiorly or exteriorly of an automotive vehicle. Still more specifically, the invention is directed to an antiglare rearview mirror mechanism for protecting the driver's eyes from glare, particularly headlight glare from following vehicles, by automatically providing a reflected image of high or low brightness depending upon the intensity of light impinging thereon.
2. Description of the Prior Art
The proper perception of traffic activity to the rear of the vehicle through the rearview mirrors is one of the essentials of driving safety. During night driving, however, the driver's visibility is seriously affected by the glare from following vehicle headlights reflected by the rearview mirrors into his eyes. The glare can reduce or disable the driver's vision not only of the rear traffic events but further of the roadway ahead.
In an attempt to minimize such glare, U.S. Pat. No. 3,740,122 to Stern discloses a rearview mirror assembly including a mirror element which is manually moved between two positions to produce reflected images of different intensity. The mirror element is retained in either position by permanent magnets attached thereto and to its housing. This prior art device is subject to the objection that it requires manual actuation, imposing an additional duty on the driver and possibly detracting his attention from driving.
The above drawback is totally absent from the automatic antiglare mirror disclosed in U.S. Pat. No. 4,078,859 to Sharett. According to this Sharett patent, a mirror element pivoted within a housing is normally spring retained in one of its operating positions. Automatic actuation of the mirror element is effected by a photocell which on sensing an increase in the intensity of light falling thereon, energizes electromagnets attached to the mirror element and to the housing. Thus energized, the electromagnets function to move the mirror element to the other operating position against the force of the spring, resulting in the attenuation of the reflected light.
This prior art automatic antiglare mirror has its own disadvantages, however. First, the spring in use must be of sufficiently heavy make to positively retain the mirror element in its normal operating position in spite of vibrations produced by the vehicle running. Thus, in the event of glare, the electromagnets must be fed with electrical energy sufficiently great to pivot the mirror element against the force of the spring.
The energy requirement of the antiglare mirror according to the Sharett patent is further augmented by the face that the electromagnets must be held energized as long as the intensity of the incident light remains high. The electrical energy fed to the electromagnets during the prolonged presence of the glare source must also be sufficiently great to overcome the force of the spring tending to return the mirror element to its normal position. In the worst case, therefore, the coils of the electromagnets may overheat or break down.
As an additional disadvantage the Sharett antiglare mirror is not adaptable for manual actuation of its mirror element. Such manual actuation, in addition to automatic actuation, adds to the utility of antiglare rearview mirrors for automative use.